The following code allows a lookup of a US ZIP code without leaving Vim. Place the cursor over a 5-digit number (the ZIP code), and choose ZipLookup from the Utilities menu. The result is then displayed at the bottom of the screen. For example, placing the cursor over "02169" should result in "02169 ==> QUINCY, MA" being displayed.

This works by accessing the USPS web site, so one needs to be online for this to work. Since the code parses the HTML code, this breaks whenever the web site code is reorganized, which seems to happen every other year or so, but can be fixed by adjusting the regexp (which may take a bit of fiddling). The code is in TCL, so one needs to use a TCL-enabled version of Vim.